Waist Size Matters

How Abdominal Fat Increases Disease Risk

More than 60 years ago, the French physician Jean Vague observed that people with larger waists had a higher risk of premature cardiovascular disease and death than people who had trimmer waists or carried more of their weight around their hips and thighs. (1) Decades later, long-term follow-up studies showed that so-called “abdominal obesity” was strongly associated with an increased risk of type 2 diabetes, cardiovascular disease and death, even after controlling for body mass index (BMI). (2,3)

Apple- and Pear-Shaped Body Types

Abdominal obesity results in an â€œapple-shapedâ€ body type, which is more common among men. Women typically accumulate fat around the hips and thighs to develop a â€œpear-shapedâ€ body type (although they can certainly develop â€œapple-shapedâ€ body types as well).

The two most common ways to measure abdominal obesity are waist circumference and waist size compared to hip size, also known as the waist-to-hip ratio. Several organizations have defined cut-points for abdominal obesity around one or both of these measurements, with different cut-points for men and women (see table).

In people who are not overweight, having a large waist may mean that they are at higher risk of health problems than someone with a trim waist.

The Nurses’ Health Study, one of the largest and longest studies to date that has measured abdominal obesity, looked at the relationship between waist size and death from heart disease, cancer, or any cause in middle-aged women. (4) At the start of the study, all 44,000 study volunteers were healthy, and all of them measured their waist size and hip size.

After 16 years, women who had reported the highest waist sizesâ€”35 inches or higherâ€”had nearly double the risk of dying from heart disease, compared to women who had reported the lowest waist sizes (less than 28 inches). (4)

Women in the group with the largest waists had a similarly high risk of death from cancer or any cause, compared with women with the smallest waists. The risks increased steadily with every added inch around the waist.

The study found that even women at a “normal weight”â€”BMI less than 25â€”were at a higher risk, if they were carrying more of that weight around their waist: Normal-weight women with a waist of 35 inches or higher had three times the risk of death from heart disease, compared to normal-weight women whose waists were smaller than 35 inches.

The Shanghai Women’s Health study found a similar relationship between abdominal fatness and risk of death from any cause in normal-weight women. (5)

What is it about abdominal fat that makes it strong marker of disease risk? The fat surrounding the liver and other abdominal organs, so-called â€œvisceral fat,â€ is very metabolically active. It releases fatty acids, inflammatory agents, and hormones that ultimately lead to higher LDL cholesterol, triglycerides, blood glucose, and blood pressure. (6)

Which Is Best: Waist or Waist-to-Hip?

Scientists have long debated which measure of abdominal fat is the best predictor of health risk: Waist size alone or waist-to-hip ratio.The research to date has been mixed. But adding up the evidence from multiple studies suggests that both methods do an equally good job of predicting health risks.

In 2007, for example, a combined analysis of fifteen prospective cohort studies found that waist-to-hip ratio and waist circumference were both associated with CVD riskâ€”and were no different from each other in predicting CVD risk. (7)

Other researchers have found that waist, waist-to-hip ratio, and BMI are similarly strong predictors of type 2 diabetes. (8,9)

The Nursesâ€™ Health Study also found that waist and waist-to-hip ratio are equally effective at predicting who was at risk of death from heart disease, cancer, or any cause. (4)

In practice, it is easier to measure and interpret waist circumference than it is to measure both waist and hip. That makes waist circumference the better choice for many settings.

Abdominal Obesity Measurement Guidelines

Organization

Measurement used

Definition of abdominal obesity

American Heart Association, National Heart, Lung and Blood Institute (10)

References

2. Ohlson LO, Larsson B, Svardsudd K, et al. The influence of body fat distribution on the incidence of diabetes mellitus. 13.5 years of follow-up of the participants in the study of men born in 1913. Diabetes. 1985;34:1055-8.

12. World Health Organization. Definition, Diagnosis, and Classification of Diabetes Mellitus and its Complications: Report of a WHO Consultation. Part I: Diagnosis and Classification of Diabetes Mellitus. Geneva: World Health Organization. 1999. Assessed on January 26, 2011.

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